(1) Field of the Invention
The invention relates to mechanical seals, and more particularly to rotary seals on shafts in high pressure pumps.
(2) Prior Art
Mechanical, rotary, or end-face seals comprise an arrangement of rotating and stationary elements disposed about a rotatable shaft, the elements being in "rubbing" contact to form a sealing face with minimum leakage therethrough. The rotating elements comprise radial planar surfaces, normal to the shaft axis, cooperating as a thrust bearing. One face is generally resiliently gasketed to a housing, and the other face is rotated with the shaft, sealed therewith by a bellows or other type of packing, permitting some axial motion to compensate for wear and play. Bearing contact between the faces is usually accomplished by spring loading one of the rotating elements.
This type of mechanical seal is found on high pressure pumps involved with refinery and chemical industry processes and where an abrasive medium is pumped, such as coal/oil slurries. Particulate buildup does cause seal-face distortion such as concavity, convexity, waviness or non-uniform contact, which distortion may also arise from shaft misalignment, improper assembly, non-uniform bolting stresses or the like, all of which contribute to leakage of the process medium and bearing and seal failure.
Other types of seals found in the prior art, in addition to the aforementioned type having the radial planar faces, are shown by U.S. Pat. No. 2,170,134, wherein a pair of packing rings with lubricant impregnated cores and pliant metallic shells are cut into sections and transformed by spinning into conical shaped packing rings. The sides however, have slits formed therealong, which can collect particulate matter.
Sealing packings, are those shown by U.S. Pat. Nos. 1,788,966 and 4,039,198. Packings, however, by virtue of their resilience, provide a radially directed force against (and away from) the shaft, when they are tightened by collars or the like. The packings can accumulate particulate matter and score the shaft. The packing gland in the U.S. Pat. No. 4,039,198 patent is of a conical shape but it is segmented, again providing places for accumulating particulate matter.
It is an object of the present invention to overcome the drawbacks of the prior art.
It is a further object of the present invention to provide a mechanical seal which will not score a rotating shaft, which will not accumulate particulate matter, and which will compensate for eccentricities of its associated rotating shaft.